sub sier(x as uinteger, y as uinteger, l as uinteger)
   if l=0 then
       locate y, x: print "*"
   else
     sier(x,y+l,l\2)
     sier(x+l,y,l\2)
     sier(x+2*l,y+l,l\2)
   end if
end sub

cls
sier(1,1,2^3)